This invention relates to cylindrical balers and more particularly to a hydraulic circuit for controlling the tension of the bale chamber defining belts and the operation of the bale discharge gate.
One well-known type of cylindrical baler comprises at least one set of longitudinally extending side-by-side belts (e.g., metal or rubber and fabric construction) supported on a plurality of transverse rollers. The belts and rollers define an expandable chamber for forming cylindrical, spirally wound bales of crops such as hay and forage. To form a bale, the crops are picked up from the ground as the baler moves across the field. When the bale reaches a predetermined diameter, it is bound by being wrapped in twine in the bale-forming chamber. The bale is then discharged onto the ground through a rear gate.
Movement of the rear gate between an open and a closed position is controlled by a pair of jacks. One jack is disposed on each side of the baler. The jacks are actuated in one direction to open the gate for discharging a completed bale and then in the other direction to close the gate for formation of another bale. The volume or size of the bale-forming chamber formed by the belts increases to accommodate the increasing bale diameter during formation. The increase in chamber volume is produced by displacing some of the belt guide rollers which are typically journalled at their ends between a pair of arms extending respectively along each sidewall of the baler. Movement of the arms to increase the diameter or volume of the bale-forming chamber is restrained to ensure that the belts are properly tensioned to compress the crop material into a tightly wrapped, spirally wound, high density roll. A high density bale is desired for harvesting efficiency, bale integrity following discharge and improved storage life.
Springs are used to restrain the movement of the belt tensioning arms. Each tension arm includes a first portion extending along the inside of the sidewall and a second portion rigidly connected thereto extending along the outside of the sidewall. The springs are mounted externally of the sidewall and are connected to the second portion of the tension arm. The springs also apply a return force to the belt tension arms when the bale is discharged. The return force restores the arms to a position corresponding to a minimum volume of the chamber used at the beginning of the bale-forming operation.
Also, in combination with the springs for biasing the chamber tensioning arms or in lieu of them, a jack may be disposed on each side of the baler and mounted between the external, second portion of the belt tension arm and a fixed point on the baler frame. During bale formation, each jack operates in a closed circuit mode in which fluid goes from one side of the jack piston to the other through a circuit which provides a suitable resistance. As a result, the jack brakes the movement of the belt tensioning arms to maintain the belts in a properly tensioned condition. When the jacks are not used in combination with springs, a hydraulic circuit for the jacks operates the jacks to return the belt tensioning arms to the position for the initiation of bale formation.
The functions performed by the jacks for controlling the rear discharge gate of the baler and the jacks for controlling the belt tensioning arms are separate and, as such, require two independent or combined hydraulic circuits for controlling the independent functions.
Balers of this general type are disclosed in U.S. Pat. Nos. 4,391,187 and 4,252,057.